فصلنامه بیماریهای گیاهی
سال پنجاه و هفتم شماره 4 (تابستان 1401)

Macrophomina phaseolina is a soil born fungal pathogen causing charcoal rot of soybean and several other plants. Disease intensity in different hosts is related to hot and dry weather condition. In order to determination of cardinal (minimum, optimum and maximum) temperatures required for mycelial growth and microsclerotial germination, three fungal isolates from soybean fields of three regions Aliabad, Gorgan and Kalaleh in Golestan province were studied in vitro. Mycelial growth and germinated microsclerotia number were recorded daily in different temperatures and data were fitted with three growth models (Beta, segmented and dent-like). Results of statistical analyses (nonlinear regression) showed that the segmented and Beta were the most suitable model for describing the relationships between mycelial growth and microsclerotial germination of this fungus, respectively. Minimum, optimum and maximum temperatures estimated for mycelial growth were 8, 34.5 and 44.3 ºC, respectively, and 8.9, 32.3 and 45.5 ºC for microsclerotial germination.

Sesame curly top virus (SeCTV) is a new species in the genus Turncurtovirus (family Geminiviridae). To date, sesame was the only natural host of the virus. During a survey for identification of geminiviruses infecting crop, vegetable or ornamental plants in south-eastern Iran, the sesame curly top virus infection of alfalfa, bean, eggplant, faba bean, blanket flower, radish and watermelon was confirmed by PCR and sequencing. The full-length genome of seven new SeCTV isolates share >97 and ~87-88% nucleotide identity with other sequences from Iran and Pakistan, respectively. An infectious clone of SeCTV was constructed, biolistically-or Rhizobium-inoculated to several host plant species and the pathogenesis of the virus was demonstrated. Results of this study indicated that, similar to known turncurtoviruses, SeCTV has a wide natural host range in Iran and among the alternative hosts, the rate of infection and severity of disease in watermelon are remarkable.

Kalhaydari is a tall, drought tolerant and rain-fed cultivar which has been a dominant rain-fed cultivar in Fars and Kohgelouyeh and Boyerahmad provinces for a long time (more than 70 years). However, this superior cultivar is susceptible to yellow rust, caused by Puccinia striiformis f. sp. tritici. Yellow rust causes a severe damage to this cultivar in high rainfall years. The aim of the present study was to transfer two seedling resistance genes (Yr5 and Yr15) and two adult plant resistance genes (Yr18 and Yr29) from standard lines to this cultivar using marker assisted backcross. In four separate breeding projects, Kalhaydari was crossed with four donor parents including Yr5/6*Avocet'S', Yr15/6*Avocet'S', Lalbahadur/Pavon and Opata 85 to transfer Yr5, Yr15, Yr18 and Yr29 genes, respectively. The first generation (F1) was backcrossed with Kalhaydari (BC1F1). In the offspring, selection for desirable genotypes was performed using markers assisted selection. Then, offspring carrying the favorable genes were entered the second backcross. The third backcross was performed using the same method. After a few more backcrosses and a selfing generation four yellow rust-resistant lines with the same genetic background, Kalhaydari cultivar, will be created. Durable resistance can be achieved using genes pyramiding.

Green basil (Ocimum basilicum L.) is a medicinal plant widely used in the food, cosmetics, and perfumery industries. Cucumber mosaic virus is one of the most common plant pathogens worldwide. In the present study, the effect of cucumber mosaic virus (strain Fny) infection on the phytochemical and physiological properties of three green basil cultivars under growth chamber conditions (21 ± 2 ° C and 16-hour light/8 hour dark period) was investigated. The plants were mechanically-inoculated in the true two-leaf stage with the virus. Mean comparison of the studied traits showed that the virus significantly reduced photosynthesis, the content of chlorophyll a and b, total chlorophyll, and total carbohydrates in the infected plants. In contrast, the content of total protein, amino acid proline, total phenol, flavonoids, and the percentage of essential oils (w/v) in infected plants was increased. The results of essential oil analysis of three basil cultivars by Gas chromatography and Gas chromatography-mass showed a significant difference in essential oil compounds between control and viral treatments of each cultivar. The compounds Camphor, Carvone, Estragole, Methyl Eugenol, Beta-caryophyllene Alpha bisabolene, and Caryophyllene oxide make up more than 70% of the essential oil content. Results of the present study indicated that viral infection causes physiological and phytochemical changes in virus-infected plants. Increasing and/or decreasing the phytochemical content and some essential oil compounds depends on the interaction of the virus and the basil cultivar and may be in line with the susceptibility or resistance of the cultivars to the virus infection.

Heterodera schachtii is the most important nematode of sugar beet worldwide. Application of organic matter can reduce populations of plant-parasitic nematodes. In this study, the inhibitory effects of creeping thistle, tall sisymbrium, liquorice, narrow-leaf plantain, wild lettuce, castor bean, French marigold, cornflower, wild safflower and arugula on sugar beet cv. Sharif and H. schachtii were investigated in two microplot experiments. The first experiment was conducted in pasteurized mixed field soil and river sand, and the second in field soil, both with an initial population of 4200 eggs/plant. Also, the effects of the treatments on nematode egg hatching and root penetration were studied in a glasshouse experiment. The results showed that adding plant powders to pasteurized soil had no significant effect on the infected sugar beet growth indices. However, except marigold, the other treatments caused a relative increase in taproot weight of 5% to 241% compared to the control. Cornflower, wild lettuce and wild safflower increased taproot weight more than twofold compared to the control. Moreover, creeping thistle, castor bean and plantain caused a relative decrease in nematode final population and reproduction factor. In field soil, castor bean, marigold, wild lettuce, cornflower and sisymbrium increased taproot weight by at least twofold, and arugula increased sugar content by 1.2-fold. The treatments had no significant effect on the nematode indices. Plantain and wild lettuce caused a relative decrease in the nematode reproduction factor. In glasshouse experiment, wild lettuce caused the greatest reduction in egg hatching and safflower reduced nematode penetration into the roots.

During a survey in 2021 a number of pepper and tomato plant samples with the begomovirus-like symptoms such as crinkled and curling leaves were collected from pepper and tomato greenhouses in three central provinces of Iran (Yazd, Isfahan and Kerman). Some weed species occurring within proximity to the greenhouse cultivated tomato crops were also sampled. To identify the Begomovirus infection in the collected samples, total DNA samples were extracted using a CTAB-based method and subjected to polymerase chain reaction (PCR)using the begomovirus degenerate primer pair BC primer and primer181V (Anfoka et al. 2005). This primer pair produced an amplicon of about 500 bp from pepper (Yazd and Kerman), tomato (Yazd) and puppet (Yazd) samples. Multiple alignment of the resulted nucleotide sequences showed that the isolates share maximum and minimum identities of 97.8 to 88.4% respectively with nucleotide sequences of chili leaf curl virus (ChiLCV) isolates reported from Oman (97.83%), Pakistan (97.83%), and India (97.64%) while they showed less than 80.2% similarity with other geminiviruses. Furthermore, a 1351bp fragment of DNA-β satellite genome was successfully amplified from pepper and tomato isolates (collected in Molabashi and Dehaghan regions in Yazd and Isfahan provinces respectively), using specific beta-satellite primer pair Beta01 / Beta02 (Cui et al., 2004). Alignment of the obtained sequences showed a very close homology to the beta satellite (ToLCB) associated with Iranian isolate of ToLCV, (MN175237.1) (Benanej et al. 2019).